Thursday, June 14, 2012

Hearing loss may change brain structure

"In the case of tinnitus, surprisingly, there were few changes to brain structure despite changes to function, suggesting that when sensory deprivation is accompanied by self-generated noise, it may be better at preserving neural tissue," says Fatima Husain.

Researchers used two different imaging modalities in studies of people with hearing loss, normal hearing, and those with hearing loss and tinnitus (ringing in the ears).

People in the hearing loss group showed structural changes in their brains.

“This suggests that functional changes due to sensory deprivation may result in long-term structural changes,” says Fatima Husain, a Beckman Institute faculty member at the University of Illinois.

The goal of the study was to investigate structural gray and white matter changes related to tinnitus and hearing loss and try to dissociate them from changes due only to hearing loss. (Credit: Fatima Husain)

“However, in the case of tinnitus, surprisingly, there were few changes to brain structure despite changes to function, suggesting that when sensory deprivation is accompanied by self-generated noise, it may be better at preserving neural tissue.”

Husain and her collaborators on the study measured neuroanatomical changes in gray and white matter in the brains of participants with only bilateral hearing loss (HL), participants who had HL and tinnitus (TIN), and a control group with normal hearing (NH) without tinnitus.

Their study, reported in the journal Brain Research, looked at neuroanatomical alterations associated with hearing loss and tinnitus.

While tinnitus is often accompanied by hearing loss, not everyone with hearing loss experiences tinnitus.

The goal of the study was to investigate structural gray and white matter changes related to tinnitus and hearing loss and try to dissociate them from changes due only to hearing loss.

“We observed that the HL group had the most profound changes in both white and gray matter relative to the other groups,” Husain says. The gray matter decreases seen in the HL group relative to the NH group were in the anterior cingulate, putamen, and middle frontal gyrus.

Two of these regions, the anterior cingulate and frontal cortex, were “also implicated in our companion study that studied functional response of the brain in the same group of subjects and points to involvement of the attention processing network.”

By dissociating the effect of tinnitus from hearing loss, the researchers concluded that “hearing loss rather than tinnitus had the greatest influence on gray and white matter alterations.”

Husain directs the Auditory Cognitive Neuroscience Lab in the Department of Speech and Hearing Science.